A variety of tube assembly clamps are known in the art for joining flanged tubing ends in sealable abutment. In a conventional design assembly, the flange rim is shaped to converge outwardly towards the flange face. The clamp, having a complementary shaped recess, is tightened around the abutting flanges, usually with nut-and-bolt pairs, such that the inwardly radially directed forces from the clamp are translated into axial forces by the inclined surface of the flanges to forceably seal the pipe ends in an abutting relationship.
Such devices are adequate for pipes which are under little or no tensile strain. However, in piping systems under tensile loads, the resulting radial forces tending to push the clamps away from the flanges require counterbalancing by overly large bolts. In addition, the holding bolts are subjected to cycle loading and fatigue failure.
With the dwindling supplies of oil and gas, offshore drilling operations in deeper and deeper waters are becoming commonplace. The tension leg platform offshore drilling and producing structure is designed for water depths which are uneconomical for fixed platforms. With such structures, a buoyant platform is anchored to the sea floor through tendons extending from the platform to the ocean bottom. The structure is given excess buoyancy and the tendons remain under a tensile load to counterbalance the excess. Connected pipe segments may be, and are preferentially used to form the tendons. Tendon axial load varies with wind, wave and current conditions and strong joints are required to withstand such cyclic loading.
In the present invention, a method and means of coupling flanged pipe ends are provided which minimizes the coupling assembly expense and the radially directed stresses on the coupling resulting from tensile axial loads.